Effect of claustrum stimulation on neurons of the contralateral medial oculomotor area, in the cat

In chloralose-anaesthetized cats, the extracellular spontaneous unitary activity was recorded from 157 neurons, located in the medial oculomotor area. 98 units were identified as projecting onto the superior colliculus. Electrical stimulations of the contralateral claustrum provoked, on 13 of these cells, an excitatory effect, lasting 10-35 ms and appearing with a latency of 20-50 ms. Full length section of the corpus callosum totally abolished the contralateral claustrum effect. The results suggest that in the cat, the claustrum may have a role in the bilateral control of the visuo-motor performance.

A symmetric Galerkin BEM for plate bending analysis

Abstract The Symmetric Galerkin Boundary Element Method is employed in thin plate bending analysis in accordance with the Love–Kirchhoff kinematical assumption. The equations are obtained through the stationary conditions of the total potential energy, written for a plate whose boundary is discretized in boundary elements. Since the matrix coefficients are made up as double integrals with high order singularities, a strategy is shown to compute these coefficients in closed form. Furthermore, in order to model the kinematical discontinuities and to weight the mechanical quantities along the boundary elements, the Lagrangian quadratic shape functions, rather than C 1 type (spline, Hermitian),…

Frictionless contact-detachment analysis: iterative linear complementarity and quadratic programming approaches.

The object of the paper concerns a consistent formulation of the classical Signorini’s theory regarding the frictionless contact problem between two elastic bodies in the hypothesis of small displacements and strains. The employment of the symmetric Galerkin boundary element method, based on boundary discrete quantities, makes it possible to distinguish two different boundary types, one in contact as the zone of potential detachment, called the real boundary, the other detached as the zone of potential contact, called the virtual boundary. The contact-detachment problem is decomposed into two sub-problems: one is purely elastic, the other regards the contact condition. Following this method…

Characteristic matrix in the bending plate analysis by SBEM

This paper deals with the thin bending plate analysis by using the symmetric approach of Boundary Element Method (SBEM). A formulation is used in which the plate boundary is discretized into boundary elements and is subjected to appropriate distributions of shear forces and couples, as well as of vertical displacement and rotations. These distributions are the causes and are modelled through appropriate shape functions, whereas the generalized effects are obtained, according to the Galerkin approach, as weighting of the displacements and the rotations, as well as of the shear forces and moments. In the equations system the algebraic operator is a symmetric matrix whose coefficients are defi…

Piastra di Kirchhoff con l'impiego del metodo simmetrico degli elementi di contorno

Modellazione lineare delle grandezze di contorno nell'analisi per sottostrutture delle piastre inflesse via SBEM

Strutture in muratura: le catene nel consolidamento

Impiego dei sottodomini via SBEM nell’analisi delle murature

Error reduction strategy in the analysis via SGBEM

Domain decomposition in the symmetric boundary element analysis

Recent developments in the symmetric boundary element method (SBEM) have shown a clear superiority of this formulation over the collocation method. Its competitiveness has been tested in comparison to the finite element method (FEM) and is manifested in several engineering problems in which internal boundaries are present, i.e. those in which the body shows a jump in the physical characteristics of the material and in which an appropriate study of the response must be used. When we work in the ambit of the SBE formulation, the body is subdivided into macroelements characterized by some relations which link the interface boundary unknowns to the external actions. These relations, valid for e…

Direct stiffness matrices of BEs in the Galerkin BEM formulation

Abstract In the analysis of an elastic two-dimensional solid body by means of the Symmetric Galerkin Boundary Element Method (SGBEM), difficulties arise in the computation of some terms of the solving system coefficients. In fact these coefficients are expressed as double integrals with singularities of order 1/ r 2 , r being the distance between the field and source points. In order to compute these coefficients a strategy based on Schwartz's distribution theory is employed. In this paper the direct stiffness matrix related to the generic node of the free boundary are computed in closed form.

Simulazione della fessura coesiva con distribuzione di molle

A multidomain approach of the SBEM in the plate bending analysis

The aim of this paper is to apply the multidomain approach of the SBEM to the plate bending analysis. The plate is subdivided into macro-elements connected each other along the interface boundary. Every macro-element is defined by an elastic relation which connects the generalized shear force and moments at the interface to the nodal displacements and rotations of the same boundary and to the loads. This approach allows a considerable reduction of the variables through a condensation process which leaves the interface kinematical unknowns, only. The assembly process may be obtained through the regularity conditions prescribed at the interface.

Problemi di contatto nel sistema suolo-struttura

Composizione e attività biologica di “idrolati” di agrumi

Gli idrolati, o acque aromatiche, sono prodotti naturali ricavati dalla distillazione di piante o parti di piante fresche che conservano intatte le loro proprietà e possono essere utilizzati a diverso scopo1. Essi sono comunemente considerati un sottoprodotto degli oli essenziali, ma in realtà, data la diversa composizione e la conseguente maggiore delicatezza, hanno un loro apprezzabile utilizzo, legato comunque al mantenimento delle proprietà delle piante da cui derivano. Nell’industria agrumaria gli idrolati sono il risultato della produzione degli oli essenziali attraverso spremitura a freddo delle bucce degli agrumi e sono considerati un rifiuto da smaltire. Lo studio della composizion…

Ottimizzazione della discretizzazione del contorno basata sulla energia residua nell'ambito del MEC simmetrico

The symmetric boundary element method for unilateral contact problems

Abstract On the basis of the boundary integral equation method, in its symmetric formulation, the frictionless unilateral contact between two elastic bodies has been studied. A boundary discretization by boundary elements leads to an algebraic formulation in the form of a linear complementarity problem. In this paper the process of contact or detachment is obtained through a step by step analysis by using generalized (weighted) quantities as the check elements: the detachment or the contact phenomenon may happen when the weighted traction or the weighted displacement is greater than the weighted cohesion or weighted minimum reference gap, respectively. The applications are performed by usin…

SBEM multidomain analysis of plate bending and stretching problems

SBEM macro-element with sides constrained by springs

The role of the claustrum in the bilateral control of frontal oculomotor neurons in the cat.

The effect of claustrum (CL) stimulation on the spontaneous unitary activity of ipsi and contralateral frontal oculomotor neurons, was studied in chloralose-anaesthetized cats. A total of 205 units was bilaterally recorded in the medial oculomotor area, homologous of the primate "frontal eye fields"; 127 neurons were identified as projecting to the superior colliculus; for 33 of these last units stimulation of the ipsilateral CL provoked an excitatory effect lasting 10-25 ms and appearing with a latency of 5-15 ms; on 8 units the excitatory effect was followed by an inhibition lasting 100-250 ms. Ninety-eight of the 127 neurons were also tested through activation of the contralateral CL: 13…

Analisi strutturale condotta con il BEM simmetrico in analogia al FEM

Nell’articolo si presenta l’approccio agli spostamenti del Metodo Simmetrico degli Elementi di Contorno attraverso una suddivisione del corpo continuo in macroelementi denominati ebem. Attraverso questo approccio, caratterizzato da una forte condensazione delle variabili, si determina per ogni e-bem una matrice capostipite a partire dalla quale viene generata la relazione costitutiva del singolo e-bem. Quest’ultima relaziona soltanto variabili all’interfaccia tra i macroelementi, e precisamente il vettore delle trazioni pesate con il vettore degli spostamenti nodali e con il vettore delle azioni esterne. Una tale strategia è molto simile a quella seguita dal Metodo degli Elementi Finiti, ma…